To light up an organic electroluminescence element at high luminance, a flow of a greater current is necessary. However, with regard to the organic EL element, in general, an anode formed of an ITO film has a sheet resistance higher than a sheet resistance of a cathode which may be formed of a metal film, an alloy film, or a metal compound film. Hence, this causes an increase in a potential gradient, and such an increase is likely to cause an increase in an in-plane variation of luminance.
In order to solve this problem, in the past, there has been proposed an organic electroluminescence element as shown in FIGS. 5(a) and (b) (document 1 [JP 2003-45674 A]). This organic electroluminescence element includes an anode 102, an organic light emitting layer 103, auxiliary electrodes 105, and a cathode 104. The anode 102 is formed on a transparent substrate 100 and is made of an ITO film. The organic light emitting layer 103 is formed on the anode 102. The auxiliary electrode 105 is formed on the anode 102, and is spaced away from the organic light emitting layer 103 at a predetermined interval. The cathode 104 is formed on the organic light emitting layer 103. In this organic electroluminescence element, light is produced in the organic light emitting layer 103 when a voltage is applied between the anode 102 and the cathode 103, and is emitted outside via the anode 102 and the transparent substrate 100.
As described in document 1, according to the organic electroluminescence element disclosed in document 1, with providing the auxiliary electrode 105, it is possible to suppress a voltage drop and generation of heat at the anode 102, and further to improve the efficiency and the luminance.
However, in the organic electroluminescence element disclosed in document 1, presence of the auxiliary electrode 105 causes an increase in an area of the non-light emission part, and such an increase may cause a decrease in an area of a light emission part defined as an overlap between the transparent substrate 100, the anode 102, the organic light emitting layer 103, and the cathode 104. In other words, in the organic electroluminescence element disclosed in document 1, the non-light emission part defined as a part other than the light emission part has an increased area. Additionally, in the aforementioned organic electroluminescence element, since the auxiliary electrode 105 has a constant width, a magnitude of a flowing current is increased at a portion of the auxiliary electrode 105 closer to a terminal part of the anode 102 (left end part of the anode 102 in FIG. 5) in a lengthwise direction of the auxiliary electrode 105 (i.e., a magnitude of a current flowing through the auxiliary electrode 105 is decreased with an increase in a distance from the terminal part of the anode 102). Hence, in the aforementioned organic electroluminescence element, a voltage drop per unit length of the auxiliary electrode 105 is increased with a decrease in a distance from the terminal part of the anode 102, and is decreased with an increase in the distance from the terminal part. Therefore, unevenness of luminance is likely to occur.